Agitation method and means

ABSTRACT

A liquid in a container is agitated by rapidly rotating the container about an axis thereof while, at the same time, allowing the container to rock about a second axis, preferably perpendicular to the first.

United States Patent Oberhauser I [54] AGITATION METHOD AND MEANS [72] inventor: Charles J. .Oberhauser, Watertown,

Mass.

[73] Assignee: Dynatech Corporation, Cambridge,

Mass.

' [22] Filed: Aug. 19, 1970 [21] Appl. No; 65,241 I [51] Int. Cl. ..'.B0lf 9/00, BOlf 11/00 [58] Field of Search....259/75, 80, 88, 176, 177, 17], 259/72, 54, 12, 29, 81, DIG. 38; 68/131,

[56] References Cited UNITED STATES PATENTS 1,227,578 5/1917 Buckner 168/207 1 1 Dec. 19, 1972 1,448,446 3/1923 Hulbert ..259/72 2,453,583 11/1948 Muller ..259/176 1,748,150 2/1930 Smellie ..68/172 1,463,626 7/1923 Marrazzo ..259/72 1,755,763 I 4/1930 Barber ..259/72 UX 1,766,310 6/1930 Schaum .....68/23 UX 2,106,609 1/1938 Krauss .68/23 UX Primary Examiner-Robert W. Jenkins Assistant ExaminervAlan 1. Cantor Attorney-Cesari and McKenna [s7] 9 ABSTRACT A liquid in a container is agitated by rapidly rotating the container about an axis thereof while, at the same time; allowing the container to rock about a second axis, preferably perpendicular to the first.

i 4 Claims, 6 Drawing Figures PATENTED DEC 19 I972 3 7 053143 SHEET 1 UF 2 CHARLES J. OBERHAUSER lnven for By CESARI 8 MrKENNA A/A..'neys PATENTED um 19 I972 SHEET 2 [IF 2 CHARLES J. OBERHAUSER By CESARI 8 McKENNA Aflomeys AGITATION METHOD AND MEANS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the mixing and agitation of materials which are capable of flow. Such materials include liquids, powders, colloids and suspensions. More particularly, it relates to a technique for mixing liquids or other flowable materials by exerting mechanical forces on a container of the material. The inventions particular applications are to the mixing of paint and the washing of clothes. Accordingly, we will describe the invention in these contexts. However, it should be understood that the agitator has broader analogous uses.

2. The Prior Art The conventional paint mixer used by the retailer shakes a closed cylindrical paint can back and forth. Thorough mixing requires at least several minutes per can provided there is sufficient head space in the can. Considerably more time is required when the head space is small.

During this time, the services which the salesman can offer other customers are restricted even though the purchase of the paint he is mixing may be, practically speaking, complete. If he does tend to other customers, he often has to interrupt his dealings with them to remove the paint can from the mixer and give it to the purchaser thereof. Alternatively, he may wait until he is through with the new customers, in which case, the purchaser of the paint may have to wait a relatively long time to obtain his purchase. Thus, conventional retail store paint shakers are costly in terms of time, both salesman time and customer time.

An improved mixer is described in my copending application, Ser. No. 840,254, filed July 9, 1969, now US. Pat. No. 3,542,344 entitled METHOD AND AP PARATUS FOR MIXING FLOWABLE MATERIALS IN CLOSED CONTAINERS, owned by the assignee of the present application. In that mixer, the paint can is rapidly accelerated and decelerated about its longitudinal axis so as to create and destroy a succession of vortexes formed in the container contents. The mixer described in said application is fast and mixes thecontents thoroughly. However, it is somewhat more expensive than the conventional shaker type of mixer. Therefore, where cost is an especially critical factor, the shaker type of mixer may be preferred, even through its results are not entirely satisfactory.

In another sense, the invention concerns the agitation of liquid in a container for other purposes such as, for example, the washing of delicate clothes. As we shall see, the present apparatus is quite superior to the usual impeller or rotary drum types of agitators found in present-day clothes washers.

SUMMARY OF THE INVENTION The present invention aims to provide an improved method for mixing liquids and other flowable materials in a container.

Another object of the invention is to provide a mechanical agitator which is able to thoroughly mix even viscous liquids in a closed container in a minimum amount of time.

Another object of the invention is to provide a paint mixer which isable to thoroughly mix a large volume of thixotropic paint in a minimum amount of time.

Another object of the invention is to provide a washing machine agitator which facilitates the thorough washing of clothes during a relatively short wash cycle.

Other objects will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combination of elements and arrangements of parts which are adapted to effect such steps, all as exemplified in the following detailed description, and the scope of the invention will be indicated in the claims.

Briefly, a container'holds the liquid or other flowable material to be agitated and mixed. The container is rotated rapidly about an axis so as to develop a vortex in the container contents whose shape depends on the rotational speed and fill level. The container is allowed to rock about another axis, preferably transverse to the first axis. Unbalance in the system causes the container to rock slightly about the transverse axis. This constitutes an angular rotation about an axis perpendicular to the axis of rotation so that the container and contents are, in effect, a gyroscope which tends to precess about a third axis perpendicular to the first two axes. The container is constrained so that it cannot precess. However, the contents are not, so that a transverse slosh wave develops which tends to feed the rocking motion. The net effect is that the container rocks back and forth with harmonic motion. The rotary and rocking motions of the container rapidly and thoroughly mix the container contents.

When the container contents have very low viscosity, e.g., water, sometimes it may be desirable to include a baffle or other type of obstruction in the container to ensure that the rotary motion of the container 'is adequately coupled to its contents so that thorough mixing results in a minimum period of time.

The present system is relatively easy and inexpensive to make as compared with the conventional agitators and mixers. This is because it only has to rotate the container in one direction at a relatively uniform speed. Therefore, it does not require clutches, brakes, eccentrics or switching circuitry found in prior comparable devices of this general type. For the same reason, the present system has a relatively long, useful life and requires a minimum amount of maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to FIG. 1 in the drawing, we will first describe the operation of the subject agitator as it mixes paint or a similar viscous or thixotropic liquid in l060ll 0209 a generally cylindrical container 10. The agitator includes a pair of spaced-apart standards 12, each having a pair of legs 12a and 12b extending fore and aft.. A generally rectangular frame 14 is positioned between standards 12 and is connected thereto by means of pivot 16 so that frame 14 is free to rock about a generally horizontal axis A. I

Container is rotatively mounted in frame 14 so that it can rotate about a generally vertical axis B. More particularly, container 10 is clamped between a pair of circular plates 18 and 22. A shaft 24 is butt welded to the center of plate 18. This shaft extends up and is journaled in a bearing 26 in the top of frame 14. Plate 18 has a depending side wall 18a which extends approximately halfway around its circumference. A curved strap 28 extends the rest of the way around the circumference of the plate. One end of strap 28 is hinged to one end of wall 18a and the other strap end is secured to the other end of wall 180 by means of a clamp 32.

Plate 22 is similarly connected to the bottom of frame 14 by a shaft 34 which is journaled in the frame bottom. Plate 22 has an upstanding wall 22a which ex tends approximately halfway around the circumference of plate 22 opposite wall 18a of plate 18. Also, a strap 36 similar to strap 28 is hinged at one end to wall 22a. Its other end is removably secured to the other end of the wall 22a by means of a clamp 38.

To load a container 10 into the agitator, the clamps 32 and 38 are released and the straps 28 and 36 swung back so that the container can he slid in between plates 18 and' 22. Thereupon, the straps 28 and 36 are en- Initially, the slosh wave W lies along the direction of the transverse axis A as seen in FIG. 2B. This produces a weight imbalance which tends to rock the container about the third axis. However, the container 10 is constrained against such movement. Nevertheless, the container and its contents are rotating so that one quarter of a revolution later, the slosh wave W is oriented so that there is more liquid on one side of the axis than there is. on the'other side of the axis as shown in FIG. 2C. This weight imbalance develops a torque about axis A which tends to rock the container clockwise about axis A, thereby. feeding the initial rocking motion. One half revolution after this, the slosh wave W causes an imbalance in-the opposite direction as shown in FIG. 2D which tends to rotate container 10 in the opposite direction, i.e., counterclockwise, about axis A, and so on. The net effect is that the container 10 and frame 14 rock back and forth with a harmonic motion.

gaged so that the container 10 is securely clamped between the plates and rotates with them.

A motor 42 is secured to the bottom of frame 14. The motor shaft (not shown) is coupled to shaft 34 so that when the motor in energized, plates 18 and 22 and the container 10 clamped between them rotate about axis B at a relatively rapid rate, on the order of 100-600 rpm.

Turning now toFlGS. 2A-2D, when container 10 is rotated about axis B, a vortex V is developed in the container contents. If this rotation were the only motion involved, eventually the contents would rotate at the same speed as the container 10 and the shape of the vortex V would depend primarily on the rotational speed, the amount of head space in the container and the characteristics of the contents. However, as a practical matter, there is also a tendency for the container 10 and frame 14 to rock about axis A. This rocking motion is given impetus initially by a slosh wave W which is developed in the container contents when the container 10 starts to rotate. In addition, there are minor imbalances in the system due to a concentration of pigment at one side of the container, for example, and other such factors.

To be more explicit, as soon as the container starts to rock even slightly about axis A, the container and itscontents tend to precess about a third axis perpendicular to axes A and B. In other words, the container and contents act, in efi'ect, like a gyroscope. However, container 10 is constrained against such precession by its connection to frame 14 so that only the contents precesses, thereby developing the slosh wave W seen in FIGS. 2B-2D.

The rocking frequency about axis A depends primarily on the geometry of the various system components such as the size and weight of container 10, dimensions of frame 14 etc. Typically, the rocking frequency is on the order of one cycle per second. What is important, however, is that the rocking is selfinduced and self-perpetuating so that it requires no additional drive means.

The rocking motion of container 10 and frame 14 will continue to grow until the container 10 and frame 14 swing as much as in each direction about axis A. Sometimes, due to space limitations, 'it may be desirable to limit the excursions of the frame. This can easily be done by connecting a resilient member 44, e.g., a spring or an elastic, between the bottom of frame 14 and a standard 12. This, in effect, restricts the amplitude of the harmonic motion imparted to container- 10 and frame 14.

The development of the slosh wave in the contents of container 10 and the constant redirecting of it due to the rocking motion of the container rapidly and thoroughly agitates and mixes the container contents.

For example, the contents of a standard five-gallon paint container can be completely mixed by rotating it at approximately 200 rpm for only 60 seconds. On the other hand, the contents of a one-gallon can of paint can be mixed even faster than this.

As seen from FIG. 1, the agitator has very few parts. Consequently, it is very easy and inexpensive to manufacture and is also easy to maintain. As a result, it suffers very little down time so that the paint store owner obtains maximum usage from it.

In addition, the'power requirements of the agitator are quite modestQOne embodiment of the paint mixer requires only a one-fifth horsepower electric motor. This low power demand is indicative of the efficiency of the agitator. The only frictional losses are in the drive and pivot bearings, plus some very nominal windage losses. All the remaining power goes directly into agitating the container contents. Consequently, the operating costs of the agitator are quite low.

The technique disclosed herein may also be applied to the washing of clothes. FIG. 3 shows an agitator suitable for this purpose. ,A housing or enclosure 50 pivotally supports an U-shaped yoke 54 by way of shafts 56 extending out sideways from the legs of the yoke and joumaled in the wall of the housing 50. An

l060ll 02l0 electric motor 58 is secured to the bottom of yoke 54. A motor shaft 58a extends through a passage 59 in the yoke into a reentrant passage 62 formed ina hollow spherical container 64. Container 64 has a removable cover 64a to provide access to its interior. The wall of reentrant passage 62 provides a convenient fastening point for the cover. More particularly, a knob 66 extending through the top of cover 64a has a threaded shaft which screws into a similarly threaded passage in the wall of the reentrant passage.

When motor 58 is energized, container 64 and its contents are rotated. Depressions 68 are formed in the wall of the container to act as internal baffles to increase the coupling between the container and the water therein. As before, the rotation of the container coupled with unbalances in the system cause the container 64 and yoke 54 to rock about the axis of shafts 56. As a result, a constantly moving slosh wave is developed within the container which agitates the water and clothes immersed therein so that the latter are thoroughly cleaned.

The motor 58 can be very small, e.g on the order of 1/10-1/30 horsepower. Alternatively, avvater turbine type of drive might be preferable because it is less expensive, even though it would require water inlet and outlet tubes.

The housing 50, yoke 54 and container 64 may be made of a suitable impact-resistant plastic such as a polycarbonate, for example. Also, container 64 can be transparent to permit observation of the washing action.

In its simplest embodiment, the washer can be filled and emptied manually, the container 64 being removable from motor shaft 58a to facilitate this. A more elaborate washer includes a pump to perform these functions and a timer to turn the unit off automatically after a predetermined time. Of course, other options commonly found in present-day rotary drum washers may be included, depending upon cost considerations and other such factors.

As can be seen from the foregoing then, the present agitator is able to mix and agitate the contents of a container in a relatively short time. The apparatus is simple to make and to operate and requires very little power. Consequently, it costs much less than prior comparable agitators and mixers of this general type.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the constructions set forth without departing from the scope of the invention, it is intended that all matter contained in the above description are shown in the accompanying drawings and shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described.

lclaim: l. The method of agitating flowable material in a container comprising the steps of A. rotating the container relatively rapidly about an axis thereof, and B. mounting the container for rocking about a second axis passing through the container and being different from the first axis, whereby the container rocks at a frequency governed primarily by the gyroscopic forces which arise due to the rapid rotation of the container and its contents. 5 2. The method of agitating flowable material as defined in claim 1 wherein the container rocks about an axis oriented substantially perpendicular to the axis of rotation.

3. The method of mixing flowable material in a container comprising the steps of A. rotating the container about an axis thereof so as to create a vortex in the container contents which is aligned generally with the axis of rotation, and

B. mounting the container for rocking about a second axis passing through the container and being oriented substantially perpendicular to the axis of rotation at a frequency governed by the gyroscopic forces which arise due to the rotation of the container and its contents so that a slosh wave is developed in the container contents which tends to precess about an axis perpendicular to the first two axes, thereby creating eddies which thoroughly mix and agitate the container contents.

4. The method of agitating flowable material in a container as defined in claim 3 wherein the container and its contents are rotated at a speed of at least 100 rpm.

5. Apparatus for agitating flowable material in a container shaped so that, when rotated, a vortex forms in the container contents comprising A. means for supporting a container for rotation about a first axis, and

B. means for pivotally supporting the support means for free rocking movement about a second axis passing through the container and being different from the first axis, and

C. means for rotating the support means about the first axis so that a vortex is created in the contents of a container in the support means, said support means also tending to rock about the second axis at a frequency governed by the gyroscopic forces which arise due to the rotation of the container and its contents, causing the vortex to shift relative to the first axis, thereby creating a precessing slosh wave in the container contents which thoroughly agitates and mixes the container contents.

6. The apparatus defined in claim 5 wherein the two axes are essentially perpendicular to one another.

7. The apparatus defined in claim 5 and further including A. a container in the support means, and

B. means in the container for increasing the coupling of the rotary motion of the container to the contents thereof.

8. Apparatus for agitating flowable material in a container shaped so that, when rotated, a vortex forms in the container contents comprising A. a base,

B. a frame,

C. means for pivotally connecting the frame to the base so that the frame can rock freely about a first axis,

D. container support means rotatively mounted on the frame, so that a container supported thereby intercepts the first axis, the axis of rotation being oriented generally perpendicular to the first axis, and

E. means for rapidly rotating the container support means about the axis of rotation so-that a vortex is formed in the contents of a container in the support means, said support means and any container therein also tending to rock about the first axis at a frequency governed primarily by the gyroscopic forces which arise due to the rotation of the container and its contents, so thatthe vortex created in the container contents tends to shift about in the container, creating a precessing slosh wave which violently agitates and mixes the container contents. v j

9. Apparatus for agitating flowable material in a container as defined in claim 8 and further including a container having one or more baffles inside the container for augmenting the mixing of the container contents.

10. Apparatus for agitating flowable material in a container as defined in claim 8 and further including resilient means operating between the frame and the base for biasing the frame to a neutral position relative to the base.

11. Apparatus for agitating flowable material comprising A. a base,

B. a frame,

C. means for pivotally connecting the frame to the base so that the frame can rock freely about a first axis,

D. a container shaped so that, when rotated, a vortex forms in the container contents rotatively mounted on the frame so as to intercept the first axis and rotate about a second axis generally perpendicular to the first axis, and a E. means for rapidly rotating the container about the second axis so that the frame rocks about the first axis at a frequency governed mostly by the conditions of dynamic imbalance which arise due to rotation of the containerand its contents.

12. The apparatus defined in claim 11 wherein the container has a removable cover.

13. Apparatus for agitating flowable material in a container shaped so that, when rotated, a vortex forms in the container contents comprising A. a base, B. afr ame,

C. means for pivotally connecting the frame to the base so that the frame can rock about a first axis, D. container support means rotatively mounted on the frame, the axis of rotation being oriented generally perpendicular to the first axis, said container support means comprising 1. a pair of spaced-apart members rotatively mounted on the frame, and v 2. means for clamping a container between the members for rotation therewith, and

E.means for rapidly rotating the container support means about the axis of rotation so that a vortex is formed in the contents of a container therein also tending to rock about the first axis so that the vortex created in the container contents tends to shift about in the container creating a precessing slosh wave which violently agitates and mixes the container contents. 14. Apparatus for agitating flowable materlal com- 1 prising A. a base,

B. a frame,

C. means for pivotally connecting the frame to the base so that the frame can rock freely about a first axis,

D. a container shaped so that, when rotated, a vortex forms in the container contents rotatively and removably mounted on the frame so as to rotate about a second axis generally perpendicular to the first axis, and

E. means for rapidly rotating the container about the second axis so that the frame rocks about the first axis at a frequency governed mostly by the conditions of dynamic imbalance which arise due to rotation of the container and its contents, said rotating means comprising an electric motor mounted on the frame with its shaft removably connected to the container.

i t III 

1. The method of agitating flowable material in a container comprising the steps of A. rotating the container relatively rapidly about an axis thereof, and B. mounting the container for rocking about a second axis passing through the container and being different from the first axis, whereby the container rocks at a frequency governed primarily by the gyroscopic forces which arise due to the rapid rotation of the container and its contents.
 2. The method of agitating flowable material as defined in claim 1 wherein the container rocks about an axis oriented substantially perpendicular to the axis of rotation.
 2. means for clamping a container between the members for rotation therewith, and E. means for rapidly rotating the container support means about the axis of rotation so that a vortex is formed in the contents of a container therein also tending to rock about the first axis so that the vortex created in the container contents tends to shift about in the container creating a precessing slosh wave which violently agitates and mixes the container contents.
 3. The method of mixing flowable material in a container comprising the steps of A. rotating the container about an axis thereof so as to create a vortex in the container contents which is aligned generally with the axis of rotation, and B. mounting the container for rocking about a second axis passing through the container and being oriented substantially perpendicular to the axis of rotation at a frequency governed by the gyroscopic forces which arise due to the rotation of the container and its contents so that a slosh wave is developed in the container contents which tends to precess about an axis perpendicular to the first two axes, thereby creating eddies which thoroughly mix and agitate the container contents.
 4. The method of agitating flowable material in a container as defined in claim 3 wherein the container and its contents are rotated at a speed of at least 100 rpm.
 5. Apparatus for agitating flowable material in a container shaped so that, when rotated, a vortex forms in the container contents comprising A. means for supporting a container for rotation about a first axis, and B. means for pivotally supporting the support means for free rocking movement about a second axis passing through the container and being different from the first axis, and C. means for rotating the support means about the first axis so that a vortex is created in the contents of a container in the support means, said support means also tending to rock about the second axis at a frequency governed by the gyroscopic forces which arise due to the rotation of the container and its contents, causing the vortex to shift relative to the first axis, thereby creating a precessing slosh wave in the container contents which thoroughly agitates and mixes the container contents.
 6. The apparatus defined in claim 5 wherein the two axes are essentially perpendicular to one another.
 7. The apparatus defined in claim 5 and further including A. a container in the support means, and B. means in the container for increasing the coupling of the rotary motion of the container to the contents thereof.
 8. Apparatus for agitating flowable material in a container shaped so that, when rotated, a vortex Forms in the container contents comprising A. a base, B. a frame, C. means for pivotally connecting the frame to the base so that the frame can rock freely about a first axis, D. container support means rotatively mounted on the frame, so that a container supported thereby intercepts the first axis, the axis of rotation being oriented generally perpendicular to the first axis, and E. means for rapidly rotating the container support means about the axis of rotation so that a vortex is formed in the contents of a container in the support means, said support means and any container therein also tending to rock about the first axis at a frequency governed primarily by the gyroscopic forces which arise due to the rotation of the container and its contents, so that the vortex created in the container contents tends to shift about in the container, creating a precessing slosh wave which violently agitates and mixes the container contents.
 9. Apparatus for agitating flowable material in a container as defined in claim 8 and further including a container having one or more baffles inside the container for augmenting the mixing of the container contents.
 10. Apparatus for agitating flowable material in a container as defined in claim 8 and further including resilient means operating between the frame and the base for biasing the frame to a neutral position relative to the base.
 11. Apparatus for agitating flowable material comprising A. a base, B. a frame, C. means for pivotally connecting the frame to the base so that the frame can rock freely about a first axis, D. a container shaped so that, when rotated, a vortex forms in the container contents rotatively mounted on the frame so as to intercept the first axis and rotate about a second axis generally perpendicular to the first axis, and E. means for rapidly rotating the container about the second axis so that the frame rocks about the first axis at a frequency governed mostly by the conditions of dynamic imbalance which arise due to rotation of the container and its contents.
 12. The apparatus defined in claim 11 wherein the container has a removable cover.
 13. Apparatus for agitating flowable material in a container shaped so that, when rotated, a vortex forms in the container contents comprising A. a base, B. a frame, C. means for pivotally connecting the frame to the base so that the frame can rock about a first axis, D. container support means rotatively mounted on the frame, the axis of rotation being oriented generally perpendicular to the first axis, said container support means comprising
 14. Apparatus for agitating flowable material comprising A. a base, B. a frame, C. means for pivotally connecting the frame to the base so that the frame can rock freely about a first axis, D. a container shaped so that, when rotated, a vortex forms in the container contents rotatively and removably mounted on the frame so as to rotate about a second axis generally perpendicular to the first axis, and E. means for rapidly rotating the container about the second axis so that the frame rocks about the first axis at a frequency governed mostly by the conditions of dynamic imbalance which arise due to rotation of the container and its contents, said rotating means comprising an electric motor mounted on the frame with its shaft removably conNected to the container. 